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Decommissioning and Other Provisions - Change in Decommissioning and Other Provision Balances (Details) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Reconciliation of changes in other provisions [abstract] |  |
Balance | $ 546 | $ 456
Liabilities incurred | 35 | 14
Liabilities settled | (37) | (43)
Accretion | (30) | 23
Acquisition of liabilities | 1 | 19
Disposition of liabilities |  | (32)
Revisions in estimated cash flows | 72 | 103
Revisions in discount rates | 36 | 16
Reversals | (6) | (1)
Change in foreign exchange rates | (4) | (7)
Balance | $ 673 | 546
Minimum |  |
Reconciliation of changes in other provisions [abstract] |  |
Increase (decrease) in discount rates, other provisions | (0.30%) |
Maximum |  |
Reconciliation of changes in other provisions [abstract] |  |
Increase (decrease) in discount rates, other provisions | (0.90%) |
IFRS 16 |  |
Reconciliation of changes in other provisions [abstract] |  |
Balance |  | 2
Decommissioning and restoration |  |
Reconciliation of changes in other provisions [abstract] |  |
Balance | $ 501 | 407
Liabilities incurred | 1 | 7
Liabilities settled | (18) | (34)
Accretion | (30) | 23
Acquisition of liabilities | 1 | 16
Disposition of liabilities |  | (23)
Revisions in estimated cash flows | 61 | 96
Revisions in discount rates | 36 | 16
Reversals | 0 | 0
Change in foreign exchange rates | (4) | (7)
Balance | 608 | 501
Decommissioning and restoration | IFRS 16 |  |
Reconciliation of changes in other provisions [abstract] |  |
Balance |  | 0
Other |  |
Reconciliation of changes in other provisions [abstract] |  |
Balance | 45 | 49
Liabilities incurred | 34 | 7
Liabilities settled | (19) | (9)
Accretion | 0 | 0
Acquisition of liabilities | 0 | 3
Disposition of liabilities |  | (9)
Revisions in estimated cash flows | 11 | 7
Revisions in discount rates | 0 | 0
Reversals | (6) | (1)
Change in foreign exchange rates | 0 | 0
Balance | $ 65 | 45
Other | IFRS 16 |  |
Reconciliation of changes in other provisions [abstract] |  |
Balance |  | $ 2

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- Definition The increase in other provisions resulting from acquisitions through business combinations. [Refer: Business combinations [member]; Other provisions] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 37 -IssueDate 2019-01-01 -Paragraph 84 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=37&code=ifrs-tx-2019-en-r&anchor=para_84&doctype=Standard -URIDate 2019-03-27 + Details
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- Definition The increase (decrease) in other provisions resulting from a change in discount rate. [Refer: Other provisions] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 37 -IssueDate 2019-01-01 -Paragraph 84 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=37&code=ifrs-tx-2019-en-r&anchor=para_84_e&doctype=Standard -URIDate 2019-03-27 + Details
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- Definition The increase (decrease) in other provisions resulting from foreign currency exchange rate changes on provisions measured in a currency different from the entity's presentation currency. [Refer: Other provisions] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 37 -IssueDate 2019-01-01 -Paragraph 84 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=37&code=ifrs-tx-2019-en-r&anchor=para_84&doctype=Standard -URIDate 2019-03-27 + Details
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